The aim of this project is the development of novel integrated optical sensors for biomedical applications. These sensors will be based on anti-resonant reflecting optical waveguides (ARROW) that allow for light propagation and guiding in low-index (liquid or gas) layers surrounded by semiconductors. Based on this principle, highly integrated instruments will be built that are compatible with fiber optic technologies and specifically avoid bulky optical setups in three dimensions involving microscopes and inefficient light coupling. This approach has several key advantages, most notably higher sensitivity, lower coupling losses and the potential for massively parallel devices due to the planar nature of the waveguide structures. Specific applications of such low-index waveguides can include fluorescence detection from single DNA molecules, highly-efficient low-volume flow cytometry, and sensitive absorption measurements of liquids containing biomolecules or gases. The implications to human health of this project range from improving fundamental understanding of DNA to more sensitive detection of potentially harmful substances in the liquid or gas phase. The specific aims of this exploratory grant are to provide the first demonstration of light guiding in low-index optical waveguides with non-solid (liquid or gas) cores and the fabrication of a first generation optical platform suitable for fluorescence measurements. The research will cover the following three areas: theory and simulation, microfabrication, and optical testing. Theoretical work will include the design of suitable ARROW waveguide structures and the calculation of detection efficiency for fluorescence in these waveguides. Microfabrication efforts will address growth and quality control of dielectric multilayer structures and fabrication of low-index channels filled with liquid or gas. Finally, prototypes will be tested with optical spectroscopy to ensure agreement with simulations and to test the robustness of the fabrication techniques. Fluorescence measurements on biological samples such as single DNA molecules will be carried out to demonstrate the potential of this integrated platform for biomedical instruments. [unreadable] [unreadable]